How do you model catalyst deactivation and incorporate it into reactor design?

Deactivation models: activity decay expressed as a = f(time, T, coke content). Common forms: first-order (da/dt = -kd*a), concentration-dependent, temperature-accelerated. Incorporate into reactor model by multiplying intrinsic rate by activity. Design implications: oversizing for end-of-run operation, determining cycle length, optimizing operating temperature (trade-off between rate and deactivation), and designing for swing operation. Moving bed or fluidized bed allows continuous regeneration. Model validation requires extensive operating data correlation.